Charles Kennedy: There is only one question the public want an answer to. And Lord Butler won't provide it

Unless the Prime Minister confronts the real issues head on his government will continue to look as though it has something to hide

On Tuesday morning, I told the Prime Minister that the Liberal Democrats would not take part in the Butler inquiry. It wasn't a decision that I took lightly - but it wasn't a decision that I agonised over either. Tony Blair had made it clear that the former cabinet secretary would be investigating only the processes of intelligence-gathering. He was not asking him to consider the fundamental questions about why we went to war in Iraq. For me, that was unacceptable.

My party voted against the military action in Iraq. I argued consistently that the case had not been made. War must always be a last resort - when all other means of resolving a crisis have failed. I said that the UN weapons inspectors should have been given time to finish their job. Today, as the failure to locate any weapons of mass destruction becomes ever more embarrassing to the Government, my concern is to get an answer to the question that millions are now asking - did we go to war on a flawed prospectus?

Since the fall of Saddam Hussein's odious regime, there has been little doubt that sooner or later the Government would have to deal with these issues. I was sceptical from the moment that the Hutton inquiry was announced that it would provide the answers. Like Lord Butler, he had been given a carefully worded remit. Lord Hutton was invited to focus narrowly on the death of Dr David Kelly - which is what he did.

Yet what was revealed in public testimony to him was tantalising. A parade of witnesses offered unprecedented glimpses of how Downing Street worked and the power of unelected advisers in the Prime Minister's immediate circle. Their evidence heightened speculation about the way that the case for war had been constructed and presented. But Hutton had been prevented from dealing with these matters given the tightness of his remit and, as late as a week ago, loyal cabinet ministers and No 10 spokesmen were ridiculing calls for a wider, independent investigation of this material.

Once again, it was George Bush who forced Downing Street into a U-turn. When the President announced his commission to get at the "facts", Blair had little option but to follow suit.

There is now such widespread distrust in the ever-changing rhetoric from government that I believe the only way to allay public suspicion is to confront the key questions head on. Yesterday's NOP poll for The Independent demonstrated the urgency. A majority of people in this country - 54 per cent - believe that Blair has been lying about this. Such an erosion of trust is undermining his office. At a time when public confidence in politicians is already low, this is damaging our democracy.

When Tony Blair telephoned me around 7pm on Monday, he had before him a letter that I had sent earlier in the day suggesting my terms for any investigation. I said it should consider the quality of the intelligence available, but that this must be combined with an analysis of the political judgements which flowed from that intelligence. What must not be allowed to happen is that the intelligence services become the scapegoats for flawed political decision-making

I didn't - and don't - underestimate the importance of finding out whether our intelligence services failed the Prime Minister. But intelligence material is rarely definitive - it is an assessment. As a privy councillor, I received briefings on intelligence material that were always accompanied by attendant "health warnings" about the sources. That is why I am determined that we should look behind the raw material at the political judgements. I am simply not prepared to support an inquiry that allows the wrong questions to distract attention from the real issues.

Blair's arguments - which I can repeat here from our exchanges in Parliament - were that "to subcontract to some committee the issue of whether it was right or wrong to go to war is not merely wrong: ultimately it is profoundly undemocratic". Listening to him in my office in the House of Commons, it was immediately clear to me that there was little point in protracted negotiations. We were fundamentally at odds.

It is a sad irony that I have spent months arguing that we are, as a nation, entitled to a full explanation. But it is also important that my decision should not be interpreted as suggesting that Butler and his committee won't provide useful insights into our intelligence-gathering mechanisms. But what this group, with such a narrow remit, meeting in private, cannot do is restore public trust and calm the current fevered political climate. We need to see that our government has nothing to hide.

I also wholly disagree with the Prime Minister. This is not a matter of "sub-contracting government decisions to a committee". In such a climate, any process that excludes politicians from scrutiny inhibits public confidence. Politicians are elected representatives who should always be willing to answer for their judgement and their competence to the people.

As a subtext to all this, the Conservative Party has done little to cover itself in glory. Its former leader was a principal cheerleader for Tony Blair in the build-up to war and Michael Howard has done nothing to dissociate himself from that view. That contradiction has undermined all his recent attempts to challenge the Prime Minister on these matters. He looks implausible. His pre-judging of Hutton and questioning of Blair's integrity before publication of the report backfired badly; while his most recent call for Blair to resign over the "45-minutes" claim is, once again, a distraction. Let's get the facts before jumping to conclusions.

While last Monday was a day of surprises, I found the Conservatives were entirely predictable. Clearly, an inquiry that limited itself to intelligence matters suits Howard just as much as Blair. They are both on tricky territory. The Tory leader has tried some shameless spin, claiming that he had negotiated changes to the wording of the remit which would allow the inquiry to address my key concerns. But Blair eliminated all possible doubts about that in his exchanges with me at Prime Minister's Questions on Wednesday.

There is one further aspect of last week that should not go unremarked. For the Prime Minister has, in effect, issued a challenge. Having blocked all independent routes to get at the truth, he is now saying that my proposals are "undemocratic". In other words, he is saying that he is accountable only through the ballot box. That may have profound consequences. For when "Hutton", "Butler", "45 minutes" and "WMD" have moved to the periphery of public consciousness and we are all focused on some other political debate (such as the disgraceful decision to push ahead with university top-up and tuition fees), the nagging questions about the war will remain. And the only way to resolve them will be the way our votes are cast.

On "Super Thursday" - 10 June - the nation's opinion will be canvassed in local, European and London mayoral elections. That may be a first test of public opinion. But the ultimate test will be the next general election. For what Tony Blair has really done this week is to tell us to take it or leave it. Forget inquiries - the people will be his judge. That decision will reverberate for months to come. And I might remind him that it did him no good in Brent East.